Page 517 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

472 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

10 –2
2,4,6-Trichlorophenol
p-Nitrophenol
Xylene
10 –3 Benzoic acid Phenol n-Butanol
Solid phase concentration, X* (mol/g) 10 –4 Hexachlorobutadiene Bromoform Dioxane Urea

Nitrobenzene

Carbon tetrachloride
–5
10
Chloroform

10 –6 Trichloroethylene Ethylene chloride
Bromochloromethane

10 –7
10 –9 10 –8 10 –7 10 –6 10 –5 10 –4 10 –3 10 –2 10 –1
Adsorbate solution concentration C* (mol/L)
FIGURE 15.10 General isotherm synthesized from specific isotherms. (Adapted from McGuire, M.J. and Suffet, I.H., The calculated net
adsorption energy concept, Chap. 4, in: Suffet, I. H. and McGuire, M. J. (Eds.), Activated Carbon Adsorption of Organics from the Aqueous
Phase, Vol. 1, Ann Arbor Science Publishers, Ann Arbor, MI, p. 108, 1980. With permission; see also SDWC (Safe Drinking Water
Committee), Drinking Water and Health, Vol. 2, National Academy Press, Washington, DC, p. 262, 1980.)

C 0
Bulk of t 2 >>0
solution
–
X(r) t >> 0
BOX 15.1
( t>>0) NOMENCLATURE ON C 0
C i
The term, C 0 , is most often used as a ‘‘starting concen-
tration,’’ e.g., with respect to distance or time, for vari-
t 1 =0
ous kinds of situations. In the case of diffusion to and
C (t=0)
i
within a particle, C 0 is designated here the adsorbate
concentration in the ‘‘bulk-of-solution,’’ e.g., as in Fig-
–
ure 15.11. In the case of a ‘‘packed bed,’’ the starting
X(r) t =0
concentration at the top of the column is also designated
r o
r C 0 , in which case the particle usually is not considered
and so the distinction in terms is not an issue. For a
Adsorbent particle in a packed bed, however, the ‘‘local’’ concen-
particle
tration at some depth, Z, is designated C,or C(Z), which
is the same as the ‘‘bulk-of-solution’’ concentration, C 0 ,
in Figure 15.11. The context in the use of C 0 gives the
Liquid film distinction. But, if the two models, e.g., packed-bed and
particle, are ‘‘linked,’’ as in a computer algorithm, the
distinction is necessary. The same ideas hold true for a
FIGURE 15.11 Concentration gradients across aqueous film and in ‘‘batch reactor.’’
solid phase from bulk of solution.